Fabrication of a 3D nano-imprint template with a conformal dry vapor deposited electron beam resist

Abstract

Nano-Imprint lithography has garnered much interest in the microlithography and nano-fabrication communities, and appears on the ITRS as a possible future lithography solution. The promise of this approach includes realization of ultimately finer features than might be possible through optical lithography and simplification of mask pattern complexity through the elimination of optical enhancements such as phase shifting and optical proximity correction. Imprinting approaches have demonstrated that sub-50nm lithography of 2D structures is possible using this approach. A potentially enabling method to enhancing imprint lithography is to add additional structures to a 2D template to form 3D profiles, thereby realizing additional benefits that can be achieved through imprinting 3D structures. In this paper we discuss fabrication of such a template, which has the potential to eliminate masking layers by allowing for two or more layers to be imprinted with a single template. A 2D template is formed on a fused silica substrate using Quantiscript's QSR-5 sterol-based vapor deposited electron beam resist, low energy e-beam lithography and reactive ion etching of the underlying substrate. Vapor deposition is especially conducive for patterning ultra thin (<50nm) layers of resist on imprint templates where high resolution structures on the order of 50-100nm are desired. After complete fabrication of the 2D template, a second resist vapor deposition, lithography and etch sequence is performed to add the 3D structures. Since the QSR-5 vapor deposited resist exhibits substrate conformal properties, uniformly thin coatings can be achieved on both 2D surfaces, allowing for high resolution trench-bottom or ridge/mesa-top lithography and processing while simultaneous protection of the initial 2D structures is realized.